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To add to the interesting threads on hoses, here's one from someone with no physics knowledge. Please be patient with this basic question!

If you open your hose valve and press the trigger on the nozzle of the hoze, I understand that thanks to the pressure of gravity from the water tower or what have you, water escapes at great velocity.

If you close your hose valve, and then go press the trigger, water still escapes at great velocity.

Why doesn't it dribble out (till the very end)? Where is the pressure coming from? Isn't the water just sitting in the hose between the valve and the nozzle?

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Water escapes at great velocity briefly.

Hoses are elastic. Some stretch more, some less, but that elastic stretch keeps the original pressure in the hose until you open the outlet. The force due to elastic hose then pushes out water, initially at the same pressure hence same high speed.

But water is leaving the hose, the water volume is dropping, hence less stretch, hence less force, hence less pressure, hence the speed rapidly drops.

A firm hose will drop speed quickly; the equivalent of a latex party balloon will go on longer, but they’ll all stop when they get back to their original unstretched volume as the elastic pressure goes to zero.

For a regular hose, this happens while there’s still a lot of water in it.

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  • $\begingroup$ Thanks. Is that elasticity intended to have this effect or is it just a byproduct of the materials chosen for flexibility, etc.? $\endgroup$ – Luke Sawczak Jun 29 '18 at 3:28

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